Product for effecting a cold chemical oxidation of copper and its alloys



Un d States Patefif" O PRODUCT FOR EFFECTING A 'COLD CHEMICAL OXIDATIONOF COPPER AND ITS ALLOYS Walter A. Mason, Minneapolis, Minn.

No Drawing. Application October 31, 1955 Serial No. 544,056

4 Claims. (Cl. 1486.24)

wherein, the character face of a matrix may be blackened by my inventionmore easily and more simply than by any other method or means now known.It is clear, however, that my invention, hereinafter specificallydisclosed, will have other uses and applications than that specificallymentioned.

In accordance with my invention, I preferably form a solution consistingof a cupric salt, selenium or tellurium, a catalyst comprising arsenictrioxide, hydrochloride acid, an alcohol, alkylaryl sulfate knowncommercially as aerosol and water.

With respect to the chemicals in the solution product aforementioned,the selenium or tellurium acts as a blackening agent for the copper,which is in solution as a copper salt. Although cupric chloride may beused, preferably I have used cupric sulfate, which is cheaper thancupric chloride, and yet which is completely compatible with themetallic surfaces to be treated, that is brass and/ or copper and theiralloys. The selenium or tellurium may be in solution as one of theoxygen acids thereof, that is selenous or selenic acid, or tellurous ortelluric acid; or in solution as a water soluble salt which may bethought of as derived from the aforementioned oxygen acids, for example,sodium or potassium tellurite. The cupric sulfate, in solution withselenous or selenic acid, or with tellurous or telluric acid, or withany of the water soluble salts of these acids, provides in solutioneither copper selenite, copper selenate, copper tellurite or coppertellurate, depending upon the extent of oxidation of the selenium ortellurium in solution. Copper selenite and copper tellurite aregenerally readily oxidized to the selenate and tellurate, respectively;and although this may occur to some extent in the solution, it at leastoccurs upon oxidation of the coated metallic surface. Therefore, it cangenerally be considered that the solution comprises either copperselenate or copper tellurate, even though as aforementioned, the copperselenium or tellurium may be in solution, at least in part, as copperselenite or copper tellurite.

In essence, it is a purpose of my invention to maintain the copperselenate or copper tellurate in solution until brought in contact withthe metallic surface to be coated, and then to controllably effect theprecipitation or plating of the copper selenate or copper tellurate ontothe metallic surface.

Copper selenate or copper tellurate is generally lllSOlll? ble in water;however, I have found that by maintaining 2,878,149 Patented Mar. I7,1958 the solution acidic the copper selenate or copper tellurate willremain in solution. For this, I provide in my novel solution product,preferably, the readily available hydro chloric acid which acts as anelectrolytic agent for maintaining the copper selenate or coppertellurate in solution as aforementioned. Any of the stronger acids mightbe used for this purpose, in addition to hydrochloric acid; but since itis preferable to have chloride in the solution, as will be subsequentlymentioned, I generally use hydrochloric acid.

The alcohol and alkylaryl sulfate components of my novel and improvedsolution act to control the plating of .the copper selenate or coppertellurate onto the metallic surface. First, with respect to the alcoholin solution, I have found that either isopropyl or methanol is to bepreferred; however, in view of the fact that other alcohols might provejust as acceptable, I do not intend the scope of my invention to belimited to isopropyl alcohol and methanol. The only specific requirementis that the alcohol be compatible with the other elements in solution sothat it will not effect a precipitation of any of the components of mysolution. As between isopropyl alcohol and methanol, I have found thatthe former is to be preferred because it will hydrolize to aid inmaintaining the solution acidic. That is, the isopropyl alcohol in theacidic solution results in an inter-action between the acid and alcoholin solution which produces an ester and which will hydrolize. Thealcohol and the alkylaryl sulfate, aerosol, act as suppressors orretarders; in other words, they slow down the plating process to producea finer grain of surface or a smoother finish. The type of finishdesired may be variable depending upon the percentage of alcohol andaerosol in relation to the amount of water, even to the extent thatthese controlling components may be omitted entirely.

As to a catalyst, I have found that arsenic trioxide effects a fastprecipitation of the copper selenate or copper tellurate and furtheracts to impart a blacker surface than if any other type of suitablecatalyst, now known, were used. It is indeed conceivable, however, thatsome catalyst equivalent in action to arsenic trioxide, with respect toits effect as a catalyst in my novel solution, may be subsequentlyfound; and I intend that such equivalent catalyst should be within thebroad scope of my invention. I believe that a cyanide catalyst would beeffective in my solution, but would be unsatisfactory because thecyanides would be generally too dangerous to use together with the acidin solution.

A specific formulation of my novel and improved solution is as follows:For each batch of solution, I have used an amount of water which mayvary between 22 and 54 gallons depending upon the dilution of solutiondesired.- For transporting my solution product, it is, of course,desirable to have a highly concentrated solution which may then bediluted as desired by the user. In this regard, it is believed that lessthan 22 gallons of water may be used; a super-saturated solution wouldbe formed using only the minimum requisite of water necessary to receivethe cupric sulfate, arsenic trioxide and selenium or tellurium insolution. Next, the selenium or tellurium, cupric sulfate, and arsenictrioxide are put into the water.

In each batch of solution, I have preferably used proportionatelybetween three and twelve pounds of cupric sulfate, between three andtwelve pounds of selenium or tellurium, and between two and six poundsof arsenic trioxide. With respect to the selenium or tellurium, Ipreferably have used, in each batch of solution, selenium dioxide, in anamount approximately equal by weight to the amount of cupric sulfate.Next, I add the hydrochloric acidin an amount approximately equal to tofluid ounces. Next, I add from between two to four pounds of aklylarylsulfate. Last, the alcohol is'a dded 9' 'copper in relation to theamount of selenium or tellurium, that one can generally use from betweenmore copper to 15% less copper than the-selenium or telluri- -um.Generally, it is preferable to include in solution more selenium ortellurium than copper because some of the copper blackening agent willreact with the surface -to be treated.

In using tellurium instead of selenium in mysoluti' on the telluriumdioxide is unsoluble in water; and a-sodium -or potassium tellurite canbe used. Preferably, I dissolve *the tellurium metal itself inhydrochloric acid beefed up with hydrogen peroxide to form telluricacid.In this respect I have used three-fourths of a fluid ounce of-hydrochloric acid, one ounce of hydrogen peroxide and-one ounce oftellurium to form approximately 1 /2 ounces of.

telluric acid. In every batch of solution product, Iwou1d use from threeto twelve pounds of telluric acid in place of the selenium dioxide. Itshould also be noted that, instead of using selenium dioxide, theselenium metal itself can be dissolved in hydrochloric acid, as withrespect to the tellurium, to form the selenous or selenic acid.

A plating or precipitation of blackened copper, copper selenate orcopper tellurate, onto the surface to be treated, brass and/or copperand their alloys, is efiected by immersing, spraying or brushing thearticle to be treated with my novel solution product, which produces thedesired blue-black or jet-black finish. There is actually a chemicalreaction or inter-action between the metallic surface to be treated, andthe solution product, so that the blackened copper precipitate isabsorbed in and be comes a part of the surface treated; therefore, itis-more than a mere coating. After coating, within twenty-four hours,the surface is oxidized and hardened. In'this respect, I have found thatwith chloride in solution, some.

copper chloride is formed which acts as a surface hardener. It might bedesirable to maintain a softersurface, and in which case, the chloridemight be left out of the solution. The alkylaryl sulfate, insolution,-n'ot-only acts as a plating control agent, but also acts-as aspread ing agent for the solution and as a detergent for.penetrating anyfilm of oil which might be retained on the surface to be plated. at

My invention has been practiced, as heretofore dis- 1 closed, and hasbeen found to accomplish all of the aforel mentioned objectives andadvantages. It will be obvious to those skilled in the art that myinvention may bemodified in many respects without departing from theessence ofmy invention; and therefore, I intend to be limited solely bythe scope of the appended claims. V

1. A solution batch consisting of in proportion approximately 3 to 12pounds of a copper blackening agent selected from the group consistingof oxygen acids and salts of selenium and tellurium, a copper salt in anamount by weight approximately equal plus or minus 15% to the weight ofcopper blackening agent, approximately 2 to 6 pounds of arsenictrioxide, approximately to fluid ounces of hydrochloric acid,approximately 2 to 4 pounds of alkylaryl sulfate, approximately 5 to 20gallons of an alcohol, and approximately 22 to 54 gallons of water.

2. A solution batch consisting of in proportion approximately 3 to 12pounds of selenium dioxide, a cupric salt in an amount by weightapproximately equal plus or minus 15% to the weight of theseleniumdioxide, approximately 2 to 6 pounds arsenic trioxide, approximately 110to 170 fluid ounces of hydrochloric acid, approxi- --mately 2 to4.-pounds of alkylaryl sulfate, approximately -5 to'20 gallons of analcohol selected from the group consisting of isopropyl alcohol andmethanol, and apl-proximately 22 to-54 gallons'of water.

' 3. A solution for coating copper and its alloys consisting essentiallyin proportion of about 3-12 pounds of a copper blackening agentselectedfrom the group consisting of oxygen acids and salts of selenium andtellurium,

a copper salt in an amount by weight approximately equal to plus orminus 15% of the weight of copper blacken'mg agent, suflicient arsenictrioxide to catalyze the solutions action on the surface to be coated, astrong acid in an amount sufficient to maintain the copper blackeningagent in solution, and solvent in an amount between about20 and 75gallons including water.

4. Asolution for coating copper and its alloys consisting essentially ofin proportion about 3-12 pounds of selenium dioxide, a cupric salt in anamount by weight approximatelyequal plus or minus 15% to the weight ofthe selenium dioxide, sufiicient arsenic trioxide to catalyze thesolutions action on the surface to be coated, hydrochloric acid in anamount sufiicient to maintain the copper blackening agent in solution,about 2 to 4 pounds of alkylarylsulfate, and solvent in an amountbetween about'20 and 75 gallons including water and an alcohol selectedfrom the group consisting of isopropyl alcohol and methanol in aproportionate amount of between 5 and 20 gallons.

"References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Chem. Abs. 43, 41481; Jr. Electro-Chemical Soc. 24, "33-91949 v

1. A SOLUTION BATCH CONSISTING OF IN PROPORTION APPROXIMATELY 3 TO 12POUNDS OF A COPPER BLACKENING AGENT SELECTED FROM THE GROUP CONSISTINGOF OXYGEN ACIDS AND SALTS OF SELENIUM AND TELLURIUM, A COPPER SALT IN ANAMOUNT BY WEIGHT APPROXIMATELY EQUAL PLUS OR MINUS 15% TO THE WEIGHT OFCOPPER BLACKENING AGENT, APPROXIMATELY 2 TO 6 POUNDS OF ARSENICTRIOXIDE, APPROXIMATELY 110 TO 170 FLUID OUNCES OF HYDROCHLORIC ACID,APPROXIMATELY 2 TO 4 POUNDS OF ALKYLARYL SURFACE, APPROXIMATELY 5 TO 20GALLONS OF AN ALCOHOL, AND APPROXIMATELY 22 TO 54 GALLONS OF WATER.